Manufacture of self-sealing bags, envelopes, and like containers



Aug. 2 1, 1956 J. w. RANDALL MANUFACTURE OF SELF-SEALING BAGS, ENVELOPES, AND LIKE CONTAINERS 2 Sheets-Sheet 1 Filed Sept. 29, 1952 Aug. 21, 1956 J. w. RANDALL 2,759,400

MANUFACTURE OF SELF-SEALING BAGS, ENVELOPES, AND LIKE CONTAINERS Filed Sept. 29, 1952 2 Sheets-Sheet 2 R v M United States Patent MANUFACTURE OF SELF-SEALING BAGS, ENVELOPES, AND LIKE CONTAINERS John William Randall, Boxmoor, Hemel Hempstead, England, assignor to John Dickinson & Co. Limited, Hemel Hempstead, England, a British company Application September 29, 1952, Serial No. 312,351 Claims priority, application Great Britain October 3, 1951 12 Claims. (CI. 93-18) The present invention relates to the manufacture of self-sealing bags, envelopes and like containers, hereinafter referred to as bags, from paper, cellulosic films and other flexible sheet material suitable for the purpose and more particularly to the manufacture of such bags from continuous webs of bag-making material.

The primary object of this invention is to provide a modified and improved method of and means for applying self-sealing adhesive substances to bags formed from materials such as glazed transparent papers, greaseproofv papers and cellulosic or other synthetic fihns having surfaces of low porosity which are normally non-receptive to or diflicult to bond with rubber latex or other adhesive substances which are suitable for use as self-sealing adhesives.

Another object of this invention is to provide a moditied and improved method of and means for producing self-sealing bags from machine-made continuous bag tubes formed from webs of bag-making materials.

it is already known that the normally non-receptive or reluctant bonding surfaces of the materials referred to above can be prepared properly to receive and bond with rubber latex and other self-sealing adhesive substances by first applying a coating of liquid gum to the surfaces and in the production of self-sealing envelopes from individual blanks it has previously been proposed to make use of this knowledge by coating selected areas of the surfaces of the envelope blanks with liquid gum prior to spraying the said selected areas with rubber latex by means of a spray in conjunction with a mask or masks through which the gum-coated areas of the envelope blanks are exposed for the reception of the sprayed latex.

It has been found, however, that while the self-sealing adhesive will bond with and satisfactorily adhere to the gum-coated surfaces, the'moisture present in the liquid gum thus applied to the surfaces of individual blanks of glazed transparent paper or films or like materials from which envelopes and other bags are commonly made causes severe curling of the material and this has hitherto constituted a serious drawback in that it interferes with the subsequent application of the self-sealing adhesive substance to the gum-coated surfaces and the feeding of the individual blanks between the travelling tapes, chains or other means for the further conveyance and processing of the blanks or envelopes formed therefrom.

In order to overcome or appreciably mitigate the above described drawbacks, self-sealing bags are produced in accordance with the present invention by a method comprising the steps of forming a web of bag-making material into a continuous bag tube for subsequently severing into tubular bag lengths, applying a coating of liquid gum to those parts of the said bag tube forming the selfthe bag tube and whilst holding the latter longitudinally extended and tensioned so that the surfaces of the bag 2,759,400 Patented Aug. 21, 1956 forming a continuous bag tube from a web of bag-making material and holding the formed bag tube longitudinally extended and tensioned, means for cutting away selected parts of the web to provide transverse openings in one wall of the formed bag tube through which parts of the inner face of the opposite wall of the formed bag tube are exposed, means for applying coatings of liquid gum to selected areas of the outer face of the cut-away wall and exposed inner face parts of the opposite wall of the formed bag tube, means for applying a self-sealing adhesive substance to selected areas of the gum-coated wall parts of the bag tube whilst it is longitudinally extended and tensioned, and means for thereafter severing the bag tube across those parts exposed through the said openings, thereby to produce separate tubular bag lengths each having a single thickness closure or sealing flap at each end thereof with the inner face of at least one of the flaps and corresponding contact area of the outer face of the cut-away bag wall coated with gum andselfsealing adhesive substance.

The method and apparatus for producing self-sealing bags in accordance with the present invention will hereinafter be further described, by way of example and without implied limitation of the scope of the invention, with reference to the accompanying drawings in which:

Fig. 1 is a plan view of a bag tube formed from a continuous web of paper or other bag-making material and provided with self-sealing adhesive substance in accordance with the method of this invention;

Fig. 2 is a plan view, drawn to a larger scale, of a tubular bag produced by severing a single bag length from the bag tube shown in Fig. 1 and sealing the bottom end of the severed bag length;

Fig. 3 is a purely diagrammatic longitudinal elevation of a continuous web-fed tubular bag making machine adapted to carry the method of this invention into effect, and

Fig. 4 is a diagrammatic plan view thereof.

Referring to Fig. 1 of the drawing, 1 indicates the continuous bag tube formed by infolding into overlapping relation the longitudinal edges of 2 of a continuous web 3 of paper or other flexbile bag-making material and 4 indicates the usual longitudinally extending seaming stripe of adhesive employed for joining together the overlapping margins of the bag tube. 5 indicates notches which are cut in the longitudinal margins of the web 3 at regular intervals and in opposite alignment to form transverse openings or slots 6 in one wall of the bag tube thereby to expose the inner faces of those portions of the opposite wall of the bag tube which will subsequently form the bottom and top end closure or sealing flaps 7 and 8 respectively of each bag length 9 severed from the bag tube 3 to form the completed bag B shown in Fig. 2. 10 indicates transverse bands or coatings of dried gum applied in liquid form to the bag tube so that the inner faces of the closure or sealing flaps exposed through the transverse openings 6 and the sealing areas.

of the outer face of the opposite cut-away wall of the bag tube, which surround the said openings 6 and will be.

covered and contacted by the folded-over end closing or sealing flaps of the formed and sealed bags, are coated with the liquid gum which subsequently dries. 11 indi cates the coatings of latex or other suitable self sealing,

adhesive substance applied to the gum-coated self-sealing faces of the top end sealing flaps 8 and corresponding sealing or contact areas of the opposite wall of the bag tube.

It will readily be appreciated that each gum coated area 10 may be entirely covered with a coating 11 of selfsealing adhesive substance, if it is desired to render both top and bottom end closure or sealing flaps 7 and 8 self sealing. Alternatively, the primary gum coatings 10 may be restricted to the self-sealing top end areas of the bag tube and the bottom end closure and sealing areas subsequently gummed or provided with some other suitable adhesive.

The method of producing self-sealing bags described above with reference to Figs. 1 and 2 may be carried into effect in a bag-making machine of the kind shown in Figs. 3 and 4 in which 12 indicates a reel from which the continuous web 3 of bag-making material is drawn by draw rolls or feed rolls 13; 14 is a breaker roll around which the web is drawn and thereby directed between a co-opera'ti'ng pair of notching rolls 15; 16 indicates an adhesive-applying unit and 17 a bag tube forming plough unit; 18 indicates the primary gum-coating unit and 19 a gum-drying unit; 21} indicates a latex-coating unit and 21 a latex-drying unit; 22 indicates secondary draw rolls; 23 indicates a bag tube severing unit; 24 are forwarding rolls; 25 is a bottom end gumming unit, while 26 indicates a flap tucking and folding unit; 43 is a delivery unit with a stacker for receiving and forming the stack S of finished bags B. F indicates in chain dot outline the longitudinal side frame members of the machine in which all of the above mentioned draw rollers and operative units are journalled or otherwise mounted as required.

The adhesive-applying unit 16 is arranged for applying the longitudinal seaming stripe 4 of gum or other adhesive to the underside of the continuous web 3 and, for this purpose, comprises a rise and fall applicator roller 27 disposed to rotate in an adhesive bath 28 and set beneath the web 3 so as to co-operate with an anvil roll 29 located above the web. The applicator roller is journalled in pivotal bell cranks 30 which are rocked by timing cams 31 so that the applicator roller is parted from its anvil roll as the notches formed in the web 3 pass therebetween, thereby to avoid soiling the anvil roll and offsetting adhesive onto the upper face of the web.

The bag tube forming plough unit 17 comprises, in known manner, a base plate 32 and co-operating plough plates 33 which serve to infold the marginal edges of the web 3 in a continuous curve, thereby forming the bag tube 1 and bringing the interrupted longitudinal adhesive seaming stripe 4 of the one inturned web margin beneath and in contact with the super-imposed web margin.

The gum-coating unit 18 and latex-coating unit 20 comprise applicator rollers 34, 34a set above the bag tube 1 so as to co-operate with anvil rollers 35, 35a respectively disposed beneath the bag tube. An arcuate re' sili'e'nt gumming pad 40 is afiixed to the periphery of the gum-coating applicator roller 34 so as selectively to apply the liquid gum coating to the required areas of the bag tube whilst avoiding contact with the intermediate parts thereof. The gumming pad 40 is supplied with liquid gum from a bath 36 through a feed roll 37 and transfer roll 38. The latex-coating applicator roller 34a is supplied with latex direct from a bath 36a and has arcuate portions 39 removed from its peripheral face, thereby ensuring that the latex coating is selectively applied to the gum-coated parts of the bag tube and withheld from the intermediate parts thereof. The gum-coating roller 34 may be made similar to the latex-coating roller 34a if so desired.

The gum drying unit 19 and latex drying unit 21 each comprises a pair of plate-like or box-like heat-transfer elements 41, 42 between which the bag tube is drawn.

Each heat-transfer element 41 or 42 may be electrically heated or heated by steam or hot air or other gaseous fluid, as so desired.

The bag-tube severing device 23, bottom end flap tucking and gumming and folding units 25, 26 and bag delivery and stacker 43 may all be of the kind commonly used in the bag-making art and need not be further described.

In carrying the method of the present invention into effect by means of the above described bag-making machine, a continuous web 3 of cellulosic films or glazed transparent paper or other suitable bag-making material, e. g. the material sold under the trade name Kristal, is drawn from the supply reel 12 and through the machine by the draw or feed rolls 13 and 22. The web first passes between the notching rolls 15 which form the notches 5 in the longitudinal margins of the web at regular intervals and at a predetermined distance apart according to the length of the bags B to be formed therefrom. The web then passes through the adhesive-applying unit 16 to receive along one margin of its underface the interrupted longitudinal seaming stripe of adhesive 4 extending between the spaced notches 5. Thereafter, the web is drawn through the bag tube forming plough unit 17 and the longitudinal margins of the web thereby infolded into overlapping relation and secured together by the adhesive seaming stripe 4, so that the oppositely aligned notches 5 are brought together to form the transverse openings or slots 6.

The formed bag tube 1 will thereupon be drawn beneath the applicator roller 34 of the gum-coating unit 18 which roller will apply the coating 10 of liquid gum to each selected slotted area of the bag tube, as above described. Each gum coating 10 is subsequently dried as the Web is drawn between the heat-transfer elements of the drying unit 19 and each gum-coated area of the bag tube subsequently passes beneath the applicator roller 34 of the latex applying unit 20 which will apply the coating 11 of latex to the said gum-coated areas of the web.

Each latex-coating 11 is dried as the web travels between the heat-transfer elements of the drying unit 21 and the bag lengths 9 are subsequently separated one by one from the bag tube as the latter passes through the severing device 23 and is transversely severed between the longitudinal edges of each opening or slot 6.

Each severed bag length 9 is passed by the forwarding rolls 24 to the end flap tucking and gumming and folding unit 25 and 26 which moi'stens the gummed surface of the bottom end flap 7 or applies fresh gum or other adhesive thereto and completes the formation of the bag by folding over and sealing the bottom end flap 7. The completed bags B so produced are delivered to the bagstacking device 27a to form the stack S.

It will be appreciated that in carrying the bag-forming method of this invention into effect, the formed bag tube is held longitudinally extended and tensioned at the time when the gum coatings 10 are applied thereto and dried thereon. Therefore, the natural tendency of the gummoistened bag-making material to curl is checked, so that the gum-coated bag tube can be drawn in substantially flat condition through the following operative units of the machine, including the latex-applying unit which applies the coatings 11 of latex to the gum-coated areas of the bag tube.

It is obvious that the above described means for applying the gum coating 10 and latex or other self-sealing adhesive coating 11 to the bag tube are adapted to function whilst the extended bag tube is travelling, thereby enabling the self-sealing bags to be produced in a completely continuous process and at a high rate of production in continuous web-fed tubular bag-making machines of basically normal construction.

The provision of the first drying unit 19 is desirable but not essential. It has been found that the gum-coated surfaces Of the bag tube will successfully receive the latex or other self-sealing adhesive substance whilst the gum is moist, providing that the bag is held longitudinally extended and tensioned. Therefore, if so desired, the drying unit 19 may be omitted and the drying of both the gum coatings and latex coatings of each bag length achieved during the passage of the longitudinally extended and tensioned web between the heat-transfer elements of the drying unit 21 which follows the latexapplying unit 20 and precedes the tube-severing device 23.

The pre-gumming of those sealing areas of the bag tube lengths to which the self-sealing adhesive substance is applied, provides a firm bonding surface for the application of the self-sealing substance and permits the use of self-sealing adhesive coatings or layers which are thinner than those normally employed when the receiving surfaces are not pre-gummed.

Furthermore, the application of the self-sealing adhesive substance by the method of the present invention and in the manner above set forth avoids adhesion between the lower or inner exposed edges of the top sealing or closure flaps of the bags and the top edges of the rear, i. e. cut-away, walls thereof, which adhesion may be expected to occur if the self-sealing adhesive substance is applied in known manner, for example, by spraying across the entire areas of the sealing surfaces.

I claim:

1. A method of producing self-sealing bags, comprising the steps of forming a web of bag-making material into a continuous, flat, parallel surfaced bag tube for subsequently severing into tubular bag lengths, cutting away portions of the said bag-making web prior to forming the said bag tube therefrom, thus to provide transverse openings in a wall of the formed bag tube, applying a coating of liquid gum to those parts of the said bag tube forming end self-sealing areas of the said bag lengths, and thereafter applying self-sealing adhesive substance to the gumcoated areas of each said bag length prior to severing it from the bag tube, both said applications being made whilst holding the parallel surfaced bag tube longitudinally extended and tensioned so that the surfaces of the said bag lengths embodied in the said bag tube support each other and are prevented from curling Where moistened by the said liquid gum applied thereto, applying part of each coating of liquid gum and part of each coating of self-sealing adhesive substance to the inner face of the opposite bag tube wall exposed through the said openings, thereafter severing the bag tube along transverse lines passing through the said openings thereby to obtain bag lengths of tubular formation with singlewall closure flaps extending from each end thereof and having the inner face of at least one of the said flaps and corresponding end contact area of the bag length coated with gum and self-sealing substance, and sealing the bottom end of the said severed tubular bag length to complete the self-sealing bag.

2. Apparatus for producing self-sealing bags from a continuous bag tube, comprising means for feeding a Web of bag-making material in a continuous length, means for forming a continuous bag tube from the said web with all surfaces parallel, means for cutting away selected parts of the longitudinal margins of the web to provide transverse openings in one Wall of the said bag tube through which openings are exposed parts of the inner face of the opposite wall of the formed bag tube means for holding said bag tube longitudinally extended and tensioned while maintaining all surfaces parallel and in mutual supporting relationship, means for applying coatings of liquid gum to selected areas of the outer face of the cut-away wall and exposed inner face parts of the said opposite wall of the formed bag tube, means for applying a self-sealing adhesive substance to selected areas of the gum-coated wall parts of the bag tube both said applications being made whilst the parallel surfaced bag tube is longitudinally extended and tensioned and the surfaces in mutual supporting relationship, and means for thereafter severing the bag tube across those parts exposed through the said openings, thereby to produce separate tubular bag lengths each having a single-wall sealing flap at each end thereof with the inner face of at least one of the said sealing flaps and corresponding contact area of the outer face of the cut-away wall coated with gum and self-sealing adhesive substance, and means for folding over and sealing the said bottom end sealing flap of each said tubular bag length to form it into a self-sealing bag.

3. Apparatus as claimed in claim 2, including means for drying each coating of liquid gum applied to the bag tube, prior to applying the said coating of self-sealing adhesive substance thereto and whilst the said gum-coated area of the said bag tube is travelling under longitudinal tension towards the said means for applying the selfsealing adhesive substance thereto.

4. Apparatus as claimed in claim 2, including means for drying the said coatings of liquid gum and self-sealing adhesive substance carried by each said bag length, prior to severing the said bag length from the bag tube and whilst the said bag tube is travelling under longitudinal tension towards the said means for severing the said tubular bag length therefrom.

5. Apparatus as claimed in claim 2, wherein the said means for forming the said bag tube include an adhesive applying unit having an adhesive-moistened applicator and co-operating anvil for applying a longitudinal seaming stripe of adhesive to a longitudinal margin of the said bag-making web, and means for periodically displacing the said applicator from its operative position so as to avoid soiling the said anvil with adhesive substance as each cut-away part of the said web margin passes between the said applicator and anvil.

6. Apparatus as claimed in claim 2, wherein the said means for applying the coatings of liquid gum to the said bag tube comprise a gum-coating unit having a displaceable gum-moistened applicator and means for periodically moving the said applicator into and out of contact with the travelling bag tube so that it applies a transverse band of liquid gum across a selected area of the travelling bag tube and then breaks contact with the said bag tube until the next selected area of the said bag tube is presented thereto to receive a coating of liquid gum.

7. Apparatus as claimed in claim 2, wherein the said means for applying the said self-sealing adhesive substance to the said gum-coated areas of the said bag tube comprise an adhesive-coating unit having a displaceable adhesive-moistened applicator and means for periodically moving the said applicator into and out of contact with the said travelling bag tube so that it applies a transverse band of the said self-sealing adhesive substance across a selected area of the said gum coated parts of the said travelling bag tube and then breaks contact with the said bag tube until the next selected area of the said bag tube is presented thereto.

8. Apparatus for producing bag lengths from which to form self-sealing bags, comprising means for feeding a web of bag-making material in a continuous length, means for forming a continuous bag tube from the said web with all surfaces parallel, means for cutting away selected parts of the longitudinal margins of the web to provide transverse openings in one wall of the said bag tube through which openings are exposed parts of the innner face of the opposite wall of the formed bag tube means for holding said bag tube longitudinally extended and tensioned while maintaining all surfaces parallel and in mutual supporting relationship, means for applying coatings of liquid gum to selected areas of the outer face of the cut-away wall and exposed inner face parts of the said opposite wall of the formed bag tube, means for applying a self-sealing adhesive substance to selected areas of the gum-coated wall parts of the said bag tube both said applications being made whilst the parallel surfaced bag tube is longitudinally extended and tensioned and the surfaces in mutual supporting relationship, and means for thereafter severing the said bag tube across those parts exposed through the said openings, thereby to produce separate tubular bag lengths each having a single wall sealing flap at each end thereof with the inner face of at least one of the said sealing flaps and corresponding contact area of the outer face of the cutaway wall coated with gum and self-sealing adhesive substance.

9. Apparatus as claimed in claim 8, including means for drying each coating of liquid gum applied to the said bag tube, prior to applying the said coating of selfsealing adhesive substance thereto and whilst the said gum-coated area of the said bag tube is travelling under longitudinal tension towards means for applying the selfsealing adhesive substance thereto.

10. Apparatus as claimed in claim 8, including means for drying the said coatings of liquid gum and self-sealing adhesive substance carried by each said bag length, prior to severing the bag length from the said bag tube and whilst the said bag tube is travelling under longitudinal tension towards the said means for severing the said bag 20 length from the said bag tube.

11. Apparatus as claimed in claim 8, wherein the said means for applying the coatings of liquid gum to the said bag tube comprise a gum-coating unit having a displaceable gum-moistened applicator, and means for periodically moving the said applicator into and out of contact with the travelling bag tube so that the said applicator applies a transverse band of liquid gum across a selected area of the said travelling bag tube and then breaks contact with the said bag tube until the next selected area of the said bag tube is presented thereto to receive a coating of liquid gum.

12. Apparatus as claimed in claim 8, wherein the said means for applying a coating of self-sealing adhesive substance to a gum-coated area of the said bag tube comprise an adhesive-coating unit having a displaceable adhesive-rnoistened applicator, and means for periodically moving the said applicator into and out of contact with the said travelling bag tube so that the said applicator applies a transverse band of the said self-sealing adhesive substance across a selected area of the said travelling bag tube and then breaks contact with the said bag tube until the next selected area of the said bag tube is presented thereto to receive a band of self-sealing adhesive substance.

References Cited in the file of this patent UNITED STATES PATENTS 619,262 Appel Feb. 14, 1899 708,001 Appel Sept. 2, 1902 1,665,611 Smith et al. Apr. 10, 1928 1,988,462 Royal Ian. 22, 1935 2,061,438 Potdevin Nov. 17, 1936 2,106,431 Jones Jan. 25, 1938 FOREIGN PATENTS 106,193 Australia Dec. 16, 1938 

1. A METHOD OF PRODUCING SELF-SEALING BAGS, COMPRISING THE STEPS OF FORMING A WEB OF BAG-MAKING MATERIAL INTO A CONTINUOUS, FLAT, PARALLEL SURFACED BAG TUBE FOR SUBSEQUENTLY SEVERING INTO TUBULAR BAG LENGTHS, CUTTING AWAY PORTIONS OF THE SAID BAG-MAKING WEB PRIOR TO FORMING THE SAID BAG TUBE THEREFROM, THUS TO PROVIDE TRANSVERSE OPENINGS IN A WALL OF THE FORMED BAG TUBE, APPLYING A COATING OF LIQUID GUM TO THOSE PARTS OF THE SAID BAG TUBE FORMING END SELF-SEALING AREAS OF THE SAID BAG LENGTHS, AND THEREAFTER APPLYING SELF-SEALING ADHESIVE SUBSTANCE TO THE GUMCOATED AREAS OF EACH SAID BAG LENGTH PRIOR TO SEVERING IT FROM THE BAG TUBE, BOTH SAID APPLICATIONS BEING MADE WHILST HOLDING THE PARALLEL SURFACED BAG TUBE LONGITUDINALLY EXTENDED AND TENSIONED SO THAT THE SURFACES OF THE SAID BAG LENGTHS EMBODIED IN THE SAID BAG TUBE SUPPORT EACH OTHER AND ARE PREVENTED FROM CURLING WHERE MOISTENED BY THE SAID LIQUID GUM APPLIED THERETO, APPLYING PART OF EACH COATING OF LIQUID GUM AND PART OF EACH COATING OF SELF-SEALING ADHESIVE SUBSTANCE TO THE INNER FACE OF THE OPPOSITE BAG TUBE WALL EXPOSED THROUGH THE SAID OPENINGS, THEREAFTER SEVERING THE SAID OPENINGS THEREBY TRANSVERSE LINES PASSING THROUGH THE SAID OPENINGS THEREBY TO OBTAIN BAG LENGTHS OF TUBULAR FORMATION WITH SINGLEWALL CLOSURE FLAPS EXTENDING FROM EACH END THEREOF AND HAVING THE INNER FACE OF AT LEAST ONE OF THE SAID FLAPS AND CORRESPONDING END CONTACT AREA OF THE BAG LENGTH COATED WITH GUM AND SELF-SEALING SUBSTANCE, AND SEALING THE BOTTOM END OF THE SAID SEVERED TUBULAR BAG LENGTH TO COMPLETE THE SELF-SEALING BAG. 